1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming method, and a storage medium.
2. Description of the Related Art
A conventional multifunction peripheral (MFP), which is an example of an image forming apparatus that forms a color image on the sheet, includes a one-drum MFP and a four-drum MFP.
A four-drum MFP includes a plurality of development units and photosensitive drums for color toners of cyan (C), magenta (M), yellow (Y), and black (K). In such a four-drum MFP, each photosensitive drum transfers an image of a corresponding color onto an intermediate transfer member. Then, each color image is transferred onto a sheet. Thus, a four-drum MFP prints the color images.
On the other hand, a one-drum MFP includes one photosensitive drum, which is sharedly used by a plurality of development units for the color toners. In such a one-drum MFP, each color toner is transferred onto an intermediate transfer member via the photosensitive drum. Thus, the one-drum MFP forms an image on the intermediate transfer member.
If the one-drum MFP is used, the number of necessary photosensitive drum(s) is smaller than that in the case of using a four-drum MFP. However, in this case, it is necessary to rotate the intermediate transfer member four revolutions to form an image of one page. That is, it takes a longer time in forming an image of one page than in the case of using a four-drum MFP.
In this regard, Japanese Patent Application Laid-Open No. 2004-128911 discusses a method for forming an image in an image forming mode called “two-image forming mode”. More specifically, in a one-image forming mode, an image of one page is transferred onto the intermediate transfer member during one revolution of the intermediate transfer member. On the other hand, in the two-image forming mode, images of two pages are transferred at the same time onto the intermediate transfer member during one revolution of the intermediate transfer member.
When such an MFP is used, in transferring image data from a controller unit to a printer unit of the MFP, the controller unit instructs the printer unit to execute an image forming operation in the two-image forming mode. If it has been instructed to execute printing in the two-image forming mode, the printer unit, at first, transfers the C toner so that images of two pages are transferred onto the intermediate transfer member.
After transferring the C toner onto the intermediate transfer member, the M, Y, and K toners are serially transferred in a page area onto which the C toner has been transferred, while rotating the intermediate transfer member. Then, each of the images of two pages, which have been formed by transferring the C, M, Y, and K toners, is transferred onto the sheet. Thus, the images are printed.
By executing printing in the above-described two-image forming mode, the images of two pages are formed during one revolution of the intermediate transfer member. Thus, the productivity can be improved.
Furthermore, in the method discussed in Japanese Patent Application Laid-Open No. 2004-128911, when the controller unit has instructed the printer unit to execute the two-image forming, if an image of the second page has not been transferred at an appropriate timing after transmitting an image of the first page, then the printer unit does not execute the instructed two-image forming and forms the image in the one-image forming mode. Accordingly, it is not necessary for the printer unit to suspend the image forming operation even when the image has not been transferred from the controller unit at an appropriate timing.
However, in the above-described image forming apparatus, if the two-image forming is temporarily unavailable due to a cause such as the delay of transfer of image data from the controller unit to the printer unit, the image is formed in the one-image forming mode instead of using the two-image forming mode. Accordingly, the productivity of subsequent image forming operations may be degraded.